The present invention relates to a method of making prefabricated relatively rigid structural panel assemblies, such as prefabricated wall, flooring and ceiling assemblies used by the prefabricated or factory built construction industry, such as the manufactured housing industry. The panels which form the surface of the panel assembly are permanently attached to reinforcing studs, joists or trusses, forming a relatively rigid prefabricated module. Closed wall modules include a pair of opposing parallel panels forming the wall surfaces and a plurality of transverse studs permanently attached to the wall boards.
The method of this invention is particularly, but not exclusively, adapted to processes for making such structural panel assemblies without the requirement of mechanical fasteners, such as nails, staples or screws to secure the panel to the structural members, which must in most cases must be covered. A problem with the manufacture of prefabricated wall, floor or ceiling panel assemblies has been that the components are not uniform. The boards used for studs, joists and trusses do not have a level or straight plane and may have other discrepancies, such as knot holes. The fibrous panels to which such support members are attached are somewhat flexible and are often warped. Thus, a wall, floor or ceiling panel, which is supported by studs, joists or trusses attached by mechanical fasteners, is generally both warped and spaced from the reinforcing members in many locations. The exposed surfaces of the mechanical fasteners must also generally be covered. This is to hide the fasteners, which may also pop out after construction because of inherent assembly and user movement and stresses resulting from the warped and imperfect components. These problems can only be partially solved in "stick built" construction, where the wall, floor or ceiling panel assemblies are built entirely on site, by selection of materials, the use of shims, etc. However, factory or pre-built construction preferably utilizes mass production techniques which do not lend themselves to such hand-made adjustments.
Another serious problem with prefabricated wall, floor and ceiling panel assemblies is the joints between adjacent panels. A wall, floor or ceiling assembly generally includes several panels which are supported by structural elements in side-by-side coplanar abutting relation. As described above, the panels and supporting structural elements or members are often irregular in shape and often warped. Further, the abutting panel edges are not precisely aligned; there are gaps between the adjacent panel edges and the adjacent edges are displaced laterally at numerous places. This problem is "solved" when using "raw" (unfinished) panels by "taping and mudding," a time consuming and expensive process. The adjacent panel edges may be beveled or tapered to form a well bridging the abutting panel edges. This depression is filled with plaster or "mud" and taped. Following drying, the joint is sanded. This process is generally repeated, at least once and the joint may take several hours or even days to dry, particularly in a humid factory, creating a manufacturing bottle neck. Where the panels are prefinished, it is generally not possible to tape and mud the joints. In such cases, the irregular seams between abutting finished panels are usually covered by batten strips. Batten strips are expensive and give an undesirable and unfinished appearance to a wall or ceiling. The batten strips generally do not exactly match the wall or ceiling and protrude from the panels. Thus, there is a need for a process which eliminates the requirement for costly and unattractive seam concealment, such as taping and mudding or batten strips.
U.S. Pat. Nos. 4,244,901 and 4,748,781, assigned to the assignee of this application, disclose methods of forming reinforced panel assemblies utilizing polyurethane foam to bond the structural support members to the panels. In the preferred embodiment, the panel is laid upon a flat support surface, the studs or support members are located on the back of the panel and clamped. A high pressure stream of a liquid foamable resin is then directed to the juncture of the support members and the panel, such that the resin foams and fills the space between the support members and the panel, permanently bonding the support members to one surface of the panel without mechanical fastening means. This method has been commercially successful in making prefabricated or factory-built structural panel assemblies; however this process is not suitable for enclosed panel construction, such as a closed wall structural assembly and does not eliminate the requirement for taping and mudding or batten strips.
The method of this invention has several advantages over the prior an and is suitable for the manufacture of enclosed panel structures, such as closed wall assemblies used by the manufactured construction industry. The disclosed method may be substantially automated and utilizes a relatively small amount of foamable resin adhesive. The method of this invention may also be used at any temperature normally encountered by the factory-built construction industry. Upon completion of the reinforced panel assembly, the assembly can be moved almost immediately using conventional mass production material handling techniques.